In experiments searching for neutrinoless double beta-decay high-purity Germanium detectors enriched in 76Ge will be used. Due to the nature of these experiments the isotopic composition of the enriched germanium is an important parameter. In order to determine the 76Ge/74Ge isotopic ratio in this new material, but also in natural and depleted samples, the feasibility of using k0- and relative standardisation neutron activation analysis for the determination of isotopic ratios was investigated. The paper will discuss the accuracy and the estimated uncertainty of both methods in general. It was found that both techniques are useful for the determination of isotopic ratios. The analysis also demonstrated that the k0-data forGe should be re-evaluated.